1. Field of the Invention
The present invention relates to communication apparatuses, communication methods, communication transmission and reception apparatuses, communication transmission and reception methods, and programs, and more particularly, to a communication apparatus, a communication method, a communication transmission and reception apparatus, a communication transmission and reception method, and a program that can be used suitably when image compression is performed for each of a plurality of line blocks.
2. Description of the Related Art
Currently, data is transferred using various types of communication, such as Internet communication. In particular, image data is transferred via networks very often. In general, image data (in particular, moving image data) whose data amount is reduced by encoding processing (compression) performed by a transmitter is transmitted to a network. The encoded data is received and decoded (decompressed) by a receiver, and image playback is performed
Moving picture experts group (MPEG) compression is the most widely known image compression technique. Recently, technological development of systems and image data transfer methods used in systems has been actively conducted in which an MPEG stream that is generated by MPEG compression and that is stored in an Internet protocol (IP) packet based on an IP is transferred via the Internet and a communication terminal, such as a personal computer, a personal digital assistant (PDA), or a cellular phone, receives the IP packet.
It is necessary to perform video on demand, streaming distribution of live images, or real-time communication, such as video conferencing or videophone systems, under the assumption that data transmission and reception is performed using terminals having different capabilities as reception terminals.
For example, transmission data transmitted from a single information transmission source is received and subjected to display processing by a reception terminal, such as a cellular phone, having a display with a lower resolution and having a central processing unit (CPU) with a lower processing capability and is also received and subjected to display processing by a reception terminal, such as a desktop personal computer, having a monitor with a higher resolution and having a CPU with a higher processing capability. As mentioned above, communication performed with various reception terminals having different processing capabilities while screen size is appropriately changed is becoming used.
As described above, as a method for allowing various reception terminals to achieve reception and display processing appropriate for respective processing capabilities, a method for hierarchically encoding data to be transmitted or received, that is, a communication system using hierarchical coding, has been suggested. In data communication using hierarchical coding, for example, encoded data to be processed by a reception terminal having a higher-resolution display and encoded data to be processed by a reception terminal having a lower-resolution display are separated so that the size or quality of an image can be changed in accordance with the separation.
For example, MPEG 4 and JPEG 2000 video streaming achieves compression/decompression using hierarchical coding. The MPEG 4 standard is scheduled to adopt a fine granularity scalability technique and to be profiled. Scalable distribution at a low bit rate and a high bit rate can be achieved with such a hierarchical coding technique. In addition, JPEG 2000 based on wavelet transform achieves, by using the characteristics of wavelet transform, packetization based on spatial resolution and hierarchical packetization based on image quality.
An example of a configuration of a communication terminal apparatus of the related art when interpolation processing is performed in accordance with MPEG or JPEG 2000 will be described with reference to FIG. 1. In FIG. 1, dotted-line arrows indicate the flow of control signals and solid-line arrows indicate the flow of data.
An image application manager 11 receives a transmission request from an application of an image source or the like, performs path control and quality of service (QoS) control over a wireless link, and controls data transmission and reception to and from the application. The image application manager 11 may also control an image input device, such as a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor. A transmission data image compressor 12 compresses image data supplied from the image application manager 11 so as to reduce the amount of image data, and outputs the compressed image data to a transmission memory 13.
The transmission memory 13 stores data received from the transmission data image compressor 12. The transmission memory 13 supports the network environment, and has a function of storing data to be transferred to another terminal in accordance with routing information. In addition, the transmission memory 13 may store reception data.
A transmission/reception controller 14 controls a media access control (MAC) protocol, such as time division multiple access (TDMA) or carrier sense multiple access (CSMA). The transmission/reception controller 14 also performs media access control called preamble sense multiple access (PSMA), which is similar to CSMA and performs packet discrimination in accordance with preamble correlation and not in accordance with carrier correlation. A transmission data generator 15 starts an encoding operation in response to a request from the transmission/reception controller 14, and generates a transmission packet by reading data stored in the transmission memory 13.
A physical layer controller 16 controls a physical layer under the control of the transmission/reception controller 14 or the transmission data generator 15. A physical layer Tx 17 starts an operation in response to a request from the physical layer controller 16, and outputs to a transmission/reception switching unit 18 a transmission packet supplied from the transmission data generator 15.
The transmission/reception switching unit 18 has a function of performing switching between data transmission and data reception. If a transmission packet is supplied from the physical layer Tx 17, the transmission/reception switching unit 18 transmits the received transmission packet via an antenna 19. If a packet is received via the antenna 19, the transmission/reception switching unit 18 supplies the received packet to a physical layer Rx20.
The physical layer Rx20 starts an operation in response to a request from the physical layer controller 16, and supplies a reception packet to a reception data separator 21. The reception data separator 21 analyses the reception packet received from the physical layer Rx20, and separates the reception packet into data necessary for the image application manager 11 and data to be transmitted to another terminal in accordance with routing.
An image decoder 22 analyzes reception data separated by the reception data separator 21, and detects a playback position for each field or each predetermined number of fields in accordance with a corresponding field number. An interpolation data storage unit 23 stores image data separated by the reception data separator 21 for each predetermined number of fields or each field. An image data input switching unit 24 appropriately selects reception data supplied from the image decoder 22 or interpolation data supplied from the interpolation data storage unit 23 in accordance with management information supplied from the reception data separator 21, and supplies the selected data to a reception data decoder 25.
A basic operation of the communication terminal apparatus shown in FIG. 1 will now be described.
Concerning data reception, the communication terminal apparatus receives data transmitted from a transmitting station, which is an external communication apparatus, via the antenna 19, the transmission/reception switching unit 18, and the physical layer Tx 17, and the reception data separator 21 separates image data from the reception data. The separated image data is decoded by the image decoder 22, and image playback is performed on a display unit or the like (not shown).
Concerning data transmission, image data is compressed by the transmission data image compressor 12, and stored in the transmission memory 13. The transmission data generator 15 reads the stored image data, and generates a transmission packet. The generated transmission packet is transmitted to a transmitting station, which is an external communication apparatus, via the physical layer Tx 17, the transmission/reception switching unit 18, and the antenna 19.
With Motion JPEG 2000 (Part 3), which is capable of supporting moving images as well as static images, hierarchized data can be stored in a file format. Moreover, as a definite proposal relating to data communication using hierarchical coding, a technique based on discrete cosine transform (DCT) has been suggested. According to this technique, for example, image data serving as communication information is subjected to DCT processing, and hierarchization in which low frequencies and high frequencies are distinguished from one another can be achieved by DCT processing. A packet that is distinguished based on hierarchization between high frequencies and low frequencies is generated, and data communication is performed using such a packet.
For distribution of such image data that has been subjected to hierarchical coding, since real-time characteristics are requested, a user datagram protocol (UDP) is used as a communication protocol on the Internet. In addition, a real-time transport protocol (RTP) is used for an upper layer, and a data format stored in a communication packet complies with a format defined for each application, that is, each encoding method.
In addition, a communication environment using various types of communication, such as local-area networks (LANs) typified by Ethernet®, optical fibers, xDSLs, power line communications, and coax networks, has been developed and widely used. In addition, the wireless LAN marketplace has significantly expanded, and wireless LAN requirements have been increasing not only in offices but also in homes. As typical examples of wireless communication, Institute of Electrical and Electronics Engineers (IEEE) 802.11, Bluetooth, an ultrawide-band (UWB) system, and the like are available. Communication speed in such communication systems has been increasing yearly. However, since the image quality of content to be transmitted using such systems has been increasing, it is difficult to transmit such image content as non-compressed data. For example, high-definition multimedia interface (HDMI) Type-A, which is gaining popularity as a transmission medium for digital content, realizes a data transfer speed of approximately 4 Gbps (that is, 165-MHz clock×24-bit data width). However, there are few systems ensuring such a bandwidth with the throughput of an application layer.
For example, a technique described in Japanese Unexamined Patent Application Publication No. 6-311494 is available.